Tuning fork type periodic switch



March 28, 1950 E PERREAULT 2,502,339

TUNING FORK TYPE PERIODIC SWITCH Filed Oct. 28, 1947 ATTORNEY Pat'ented Mar. 28, 1950 TUNING rom: ma rnaromc SWITCH George E. Perreault, White Plains, N. Y., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application October 28, 1947, Serial No. 782,528

claims. (ci. 20o-9o) This invention relates to electrical relays and more particularly to relays of the tuning fork type.

The object of the invention is to provide an improved relay of the tuning fork type.

A feature of the invention resides in contact means provided in the relay.

Another feature resides in a supporting structure for a contact.

Another feature resides in a iloating supporting structure for the tuning fork assembly.

In the drawing:

Fig. 1 is a view in perspective of a relay embodying this invention and with an operating coil exterior of the casing of the relay;

Fig. 2 is an enlarged view, in perspective and partly in section, of the relay Fig. 3 is a front view, partly in-section, of a portion of the structure shown in Fig. 2;

Fig. 4 is a side view,y partly in section, of the portion of the structure shown in Fig. 3; l i Fig. 5 is a side view, partly in section, of the upper portion` of the relay shown in Fig. 2; and

Fig. 6 is a view in cross-section of the relay and y taken on the line 6--6 in Fig. 4.

The relay of this invention comprises a. tubular casing 1 having an upper closed end 8. The casing 'I is supported endwise on a plug 9 in which the tines I4 and I5 are welded to and held inspaced relation by an apertured metal block I6 which i'orms the closed end of the tuning fork structure, the other end being free to move when' the tines I4 and I5 are vibrated. The tine' I4 is held in spaced relation with the conducting bar I2 by an apertured spacer plate I1. The closed end portion of the tuning fork structure I3 is sup- 'ported near the upper portion of the conducting bar I2 and so that the tines I4 and I5 extend transverse aperture 20 formed in the plug 9 servesl to hold the conducting bar I2 iloating in the plug 9.- It will be seen that the lower end oi the conducting bar I2 is not rigidly held in the plug 9 has angularly extending spaced leg members 24 t extending into tight frictional engagement with inner surfaces of the casing l. The spider-type supporting plate 23 rests loosely between the upper end of the tuning fork structure I3 and a bent retainer pin 25 and is held against undue upward movement on the conducting bar I2 by means of the bent retainer pin 25 extending transversely through the conducting bar I2 and above the spider-type supporting plate 23. It will be seen that the upper portion of the conducting bar I2 is not rigidly held but is permitted to move within the limitations of the relatively large aperture 22 and that the upper portion of the conducting bar I2 and the upper portion of the tuning fork structure I3 are, in effect, floatably supported in the spider-type supporting plate 23.

A permanentmagnet 26 is mounted on .the conducting bar I2 in the vicinity of and below the free ends of the tines I4 and I5. A pole-piece 21 of magnetic material extends from one end of the permanent magnet 26 and into the space 28 between the free ends of the tines I4 and I5 to maintain a magnetic eld between the free ends of the tines I4 and I5. The pole-piece 2.' is equipped with a shading coil 29 comprising a plurality of ring-like plates 30 of copper or other electrical conducting material, the pole-piece 2'I extending through the central apertures in the ring-like plates 30. The function of the shading coil 29 is to produce eddy currents to bring the Q of the tuning fork of the switch to a required value.

'I'he tines I4 and I5 may be set in Vibration through suitable energization of an operating coil 3| mounted exterior of the casing l and extending around the casing 1. A

Tuning bars 32 andA 33 are provided on the tines I4 and I5 respectively in order that the tines I4 and I5 may be tuned as required to vibrate at a predetermined frequency. The tuning bar in each case is a place of wire mounted on the tine and extending laterally across the tine and has free end portions 34 and 35 extending outwardly beasoaaso yond edge portions of the tine. The tuning bars 32 and 33 are located near the free ends of the respective tines I4 and I5 and each tuning bar forms, in effect, a loading member on the tine. By bending the free ends 34 and 35 of a tuning `bar to make the free ends 34 and 35 extend in various angular directions relative to the tine the loading effect and hence the frequency of the tine may be changed as required. More than one tuning bar may be used on each tine.

The tumng bar 33 on the tine I5 is utilized as a contact piece and is moved by action of the tine I5 relative to a spring wire contact 36, one end of which is secured to a strip 31 of conducting material.

The strip 31 of conducting material has a portion 38 embedded in an insulating block 39 mounted on a beam 43, spaced arm portions 4I and 42 of the beam 40 being embedded in the insulating block 39 and in spaced relation with the strip 31 as shown clearly in Fig. 6. As shown in Fig. 2 the beam 40 is mounted at one end on the upper portion of the tuning fork structure I3 and extends downwardly therefrom almost to the plug 9. The upper end portion of the beam 4U is held in place by screws 43 and 44 and is spaced from the tine I5 by an apertured spacer plate 45 disposed between the beam 40 and the tine I5. The screws 43 and 44 as shown in Fig. 5 extend through apertures in the beam 40, the spacer plate 45, the tine I5, spacer block I6, tine I4, spacer plate I1 and into screw-threaded engagement with the conducting bar I2. An elongated aperture 46 as shown in Figs. 2 and 3 is formed in the beam 40 to create the spaced arm portions 4I and 42 and to provide a space for accommodation of the strip 31 and the spring wire contact 36. The elongated aperture 46 in the beam 40 is deiined by an elongated boss 41 formed on portions of the spaced arm portions 4I and 42 and at points where the spaced arm portions 4I and 42 terminate. The boss 41l serves to strengthen the arm portions 4I and 42. The beam 4I) extends in spaced relation with and alongside the tine I5 and across the position of the tuning bar 33. At points where the arm portions 4I and 42 cross over the position of the tuning bar 33 the arm portions 4I and 42 are bent outwardly to provide offset portions 49 and 49 respectively to avoid engagement with the tuning bar 33 and allow operating space for the tuning bar 33 when the tine I5 is vibrating.

The lower end portion 5B of the beam 40 is movably supported on an adjustment screw 5I which is in screw-threaded engagement with the conducting bar I2 and a lock nut 52 bearing on an apertured conducting plate 53 in con tact With the conducting bar I2. The conducting plate 53 is equipped with a lug 54 which is electrically connected through a lead wire 55 with the pin-type terminal III. A spring 56 is disposed between the lower end portion 53 of the beam 40 and the lock nut 52. By suitably turning the adjustment screw 5I the lower end portion 5l of the beam 40 may be moved relative to the conducting bar I2. The lock nut 52 operates to hold the adjustment screw 5I in adjusted position and holds the apertured plate 53 `pressed against the conducting bar I2.

The strip 31 oi conducting material has a bent lower end portion 51 electrically connected through a lead wire 58 with the pin-type terminal II. The upper end portion of the strip 31 terminates in an L-shaped ilnger portion 59, the

' shorter arm portion 63 of which extends over a portion of the tree end of the tine Il and almost to the tuning bar 33. The spring wire contact 3l is secured at'one end 6I to the strip 31 and extends over the finger portion 53 and the arm portion 63 and from thence to a position overlying the tuning bar 33. The spring wire contact 36 is pretensioned toward the tuning bar 33 but is normally held in spaced relation with the tuning bar 33 by the shorter rm portion 60 of the L-shaped ilnger portion 5l. When the tine I5 is vibrated it moves the tuning bar 33 toward and away from the free end portion of the spring wire contact 36. During part of one-half cycle ot movement of the tine I5 the tuning bar 33 makes contact with the free end portion of the spring wire contact 33 and flexes the spring wire contact 36. When the tine I5 swings back in its other half cycle of movement to carry the tuning bar 33 away from the spring wire contact 36 the shorter arm portion 63 of the L-shaped finger portion 59 serves as a stop v to prevent the spring wire contact 36 from completely following the movement of the tuning bar 33. When the tuning -bar 33 is in contact with the spring wire contact 36 the circuit through the relay is as follows: pin-type terminal III, lead wire 55, lug 54, conducting plate 53, conducting bar I2, closed end of tuning fork I3, tine I5, tuning bar 33, spring wire contact 36, strip 31, lead wire 58 to pin-type terminal II.

As above mentioned the tuning bars 32 and 33 maybe adjusted to tune the respective tines I4 and I5 to a precise required frequency by bending free ends of the tuning bars 32 and 33 to make the free end portions 34 and 35 extend more or less angularly with respect to the tine on which the tuning bar is secured, possible diierent directions of bending of the free end portions of a tuning bar being indicated by dotted lines 52 in Fig. 3.

The adjustment screw 5I may be adjusted to change the normal spacing of the spring wire contact 36 relative to the tuning bar 33. The casing 1 may be removed from the plug 9 to provide access to the parts housed inthe casing 1 but is normally held against undue removal by inward embossings 63 formed in the lower end of the casing 1 and pressed into recesses 64 formed in the plug 9.

The relay shown in the drawing is equipped with the pin-type terminals I0 and Il so that it may be readily mounted in a supporting socket, not shown, but having jack-type terminals to receivethe pin-type terminals I0 and II. The

tines I4 and I5 are made from bar stock of metal composition as follows:

Nickel 42 Chromium 4.5 or 5.5 or 6.5 Titanium 2.5 Carbon .06

. Manganese .4 Silicon ,5 Aluminum--- .4

Iron, the remainder.

The tines made of a metal composition as above set forth are heat treated.

All three of these compositions have a pos` then heating to a lower temperature for the time required to cause precipitation of the desired amount of the hardening phase. By varying the time and temperature of this last heating step, the temperature coeiicient of elastic modulus can be varied within limits. The alloy containing 6.5 per cent chromium can have its temperature coeiicient of elastic modulus varied between and '-10 parts per million per degree centigrade by this method. Similarly, the alloy containing 5.5 per cent chromium can have its coefficient varied between -10 and +10 parts per million per degree centigrade, and the alloy containing 4.5 per cent chromium can have its coefficient varied between +10 and +30 parts per million per degree centigrade.

Since the coeicient of elastic modulus can be varied without varying the coeiicient of expansion, it is possible with various mechanical shapes to balance the two coefficients so that a temperature coeiiicient of frequency vibration can be produced which is substantially zero.

It is preferable to have the spacer block IB, the apertured spacer plate Il and the apertured spacer plate made of material having the same temperature coelcient of expansion as the material of the tines I4 and I5.

The conducting bar I2 is supported floatably so that under extreme temperature changes differences in expansion between the casing 'I and plug 9 and the conducting bar I2 will not cause forces which would bend the conducting bar I2 thus affecting the magnetic gaps between the tines I4 and I5 and the pole-piece 21 or the contact gap between the contact wire 36 and the tuning bar 33.

The conducting bar I2 is supported floatably also to prevent bending forces being transmitted to the conducting bar I2 by the assembly of the casing I to the plug 9 or by forces applied to the casing 1 in handling the relay when it is plugged in or out of its socket in use. The reason for floating conducting bar I2 is to prevent under temperature variations expansion stresses which would cause gap adjustment changes of the tines to the pole-piece 21 which would in turn cause a change in frequency. Also to prevent changes in the gap between wire 36 and contact 33 which would in turn cause a change in sensitivity of the relay.

Assuming that the operating coil 3l is energized with a current of required frequency and strength to set the tines I 4 and I5 in Vibration the tuning bar 33 will be moved in a series of movements into and out of Contact with the spring wire contact 36.

What is claimed is:

1. A tuning fork-type switch comprising a vibratile tine, means to vibrate said tine, an adjustably supported beam extending alongside and in spaced relation with said tine, spaced arms on said beam extending in parallel lrelation with each other, a block of insulating material supported' by said arms and embracing said arms and extending across. the space between said arms, a metal strip supported by and extending through and from `said block and into the space between said arms and a spring wire supported on said metal strip and extending into the path of movement of said vibratile tine.

2. A tuning fork-type switch comprising a vibratile tine, a contact on said tine, means to vibrate said tine, a beam secured at one end to an end portion of the tuning fork structure vand extending alongside and in spaced relation with said vibratile tine, spaced arms on said beam extending in parallel relation with each other, a block of insulating material secured to said arms and extending across the space between said arms, a conducting strip supported in and extending from said block and into the space between said arms and a spring wire secured at one end to said conducting strip and having a free end portion extending beyond said conducting strip and into the path of movement of said contact on said tine.

3. A tuning fork-type switch comprising a vibratile tine, a tuning bar of conducting material supported on said tine and extending across said tine, means to operate said tine, a beam secured at one end and extending alongside and in spaced relation with said tine and across the position of said tuning bar, spaced arms on said beam extending in parallel relation with each other and having offset portions in -by-pass of said tuning bar, a` block of insulating material secured to and supported by said arms and extending across the space between said arms, a conducting strip supported in said block and in spaced relation with said arms, an L-shaped linger portion on said conducting strip extending into the space between said arms and a spring wire contact secured at one end to said conducting strip and resting on said L-shaped linger portion and extending beyond said L-shaped finger portion and into the path of movement of said turning bar on said tine.

4. An electrical switch comprising a tubular casing, a tuning fork structure housed in said tubular casing, a plug in one end of said tubular casing, a conducting bar loosely supported at one end in said plug and extending into said tubular casing and alongside said tuning fork structure, means securing the closed end portion of said tuning fork structure to an adjacent end portion of said conducting bar and a spider-type plate of spring sheet material loosely supported on the closed end portion of said tuning fork structure and said conducting bar, said spidertype plate having formed therein a relatively large aperture through which said conducting bar extends and having leg members in frictional engagement with the inner surface of said tubular casing.

5. A tuning fork-type relay comprising a pair of spaced vibratile tines, electrically energizable means to vibrate said tines, a permanent magnet, a pole-piece extending from said permanent magnet into the space between said tines, said permanent magnet and said pole-piece producing a magnetic ileld for said tines and a shading coil means supported on and encircling said pole-piece for producing eddy currents to bring the Q of the relay to a required value.

GEORGE E. PERREAULT.

REFERENCES CITED ,The following references are of record in the -iile of this patent:

UNITED STATES PATENTS Number Name Date 200,993 Edison Mar. 5, 18'18 1,943,240` Lear Jan. 9, 1934 2,049,310 Nulsen et al July 28, 1936 2,243,920 Phillips June 3, 1941 2,339,973 Aust Jan. 25, 1944 

